1. Field of the Invention
The present invention relates to a brazing apparatus, and particularly to a brazing apparatus capable of controlling temperature factors which influence the quality of brazing.
2. Description of the Background Art
FIG. 8 is a side view schematically showing a heating and brazing filler metal supply station in a conventional automatic brazing apparatus and FIG. 9 is a plan view of the automatic brazing apparatus shown in FIG. 8. Referring to these diagrams, the automatic brazing apparatus comprises a brazing jig unit A for clamping and accurately positioning articles to be joined together, a preheating burner unit B, a heating and brazing filler metal supply unit C, and a brazing filler metal wire and combustion gas supply unit D.
In the brazing jig unit A, a driving motor 38 and an index gear 37 are fixed under a brazing apparatus fixing table 51; the driving motor 38 is for intermittently driving an index table 36 and the index gear 37 is connected to the driving shaft of the driving motor 38 to accurately position the index table 36. An air pipe 73 for supplying compressed air to a driving source for driving the jig clamp etc. is vertically fixed in the center of the index table 36 provided on the jig table. The air pipe 73 is rotatably connected to the index table 36 through seal rings 35, with O-ring seals fitted around the air pipe 73.
A jig 75 for coaxially clamping articles 71 and 72 to be joined together is disposed on the index table 36. The preheating burner unit B includes a preheating burner 39 which can move forward and backward toward and away from the center of the index table 36. In the heating and brazing filler metal supply unit C, a driving cylinder 48, fixed on the brazing apparatus fixing table 51, and a brazing unit frame 47 are coupled together, and the brazing unit frame 47 is disposed on a pair of guide rails 76 so that it can move forward and backward toward and away from the center of the index table 36.
A forked gas nozzle 43 having two prongs as a burner 42, is connected to a gas pipe 77 and attached to the moving frame 50 to protrude toward the index table 36. Plural pairs of heating torches 69 are attached to the prongs of the gas nozzle 43, each pair of heating torches 69 facing toward each other. Nozzle driving cylinders 45 are attached to a mount fitting 59 on the brazing unit frame 47 in such a manner that they can be adjusted for angle. Brazing filler metal supply nozzles 44 are attached to the nozzle driving cylinders 45, with their tips aimed at the central point of the pieces heated by the heating torches 69.
In the brazing filler metal and combustion gas supply unit D, the nozzle driving cylinders (brazing filler metal wire cylinders) 45 are driven to move the brazing filler metal supply nozzles 44 toward the brazed portion of the articles 71 and 72 to be joined. Then given amounts of brazing filler metal wires are fed by a wire supply motor 52 from brazing filler metal wire reels 58a and 58b. A mixture of combustible gas and burning-supporting gas (oxygen) mixed in a given ratio is supplied as the combustion gas.
Next, the brazing operation is briefly described referring to FIGS. 8 and 9.
First, the articles 71 and 72 to be brazed together are introduced and held by the jig 75, and then the index table 36 rotates 90xc2x0, clockwise in FIG. 9, to bring them to the stage of the preheating burner unit B. Then the preheating burner 39 moves forward to locate its prongs around the articles 71 and 72 and the preheating burner 39 preheats them. After preheating, the preheating burner 39 moves backward, and the index table 36 further rotates 90xc2x0 clockwise to bring the preheated articles 71 and 72 to the stage of the heating and brazing filler metal supply unit C. Then the gas nozzle 43 is moved forward in given timing and starts heating the joined portion of the articles 71 and 72 with xe2x80x9chighxe2x80x9d flames.
The brazing filler metal supply nozzles 44 start moving forward somewhat after the gas nozzle 43 has began heating. Further later, the brazing filler metal wires 46 are supplied from the brazing filler metal supply nozzles 44 in given timing to the joined portion of the articles 71 and 72 and then brazing is performed. The gas nozzle 43 heats the joined portion for a given time period, and then the flames are changed from xe2x80x9chighxe2x80x9d to xe2x80x9clow,xe2x80x9d and the burner 42 retreats when the low flame period ends. The brazing operation thus ends. The brazing filler metal supply nozzles 44 are withdrawn around when the flames of the gas nozzle 43 are changed from xe2x80x9chighxe2x80x9d to xe2x80x9clow.xe2x80x9d
After brazing, the index table 36 further rotates 90xc2x0 and the joined articles 71 and 72 are taken out as a brazed product. As explained so far, a set of articles to be brazed together are introduced each time the index table 36 rotates 90xc2x0 and are brazed through the preheating, brazing, and exit stages. In practice, a plurality of sets of articles to be brazed are sequentially introduced each time the index table 36 rotates 90xc2x0 and are brazed in parallel through the stages.
The conventional brazing apparatus shown above encounters no particular problem when the temperature of the articles introduced to be brazed and the temperature in the atmosphere stay constant. However, inferior brazing may be caused when such temperatures vary at changes of the season, or vary when the operation is started at the beginning of the working hours, during the operation, or when the operation is restarted after interruption. That is to say, when the articles to be brazed are heated with a constant amount of heating in the preheating and heating processes, variations of such conditions cause the articles to attain varied temperatures during brazing, which would result in unstable brazing quality.
Even if the amount of preheating and the amount of heating can be varied to control the heating depending on the articles to be brazed, it is still difficult to keep the temperature rise of the articles constant since accurate information for controlling the amounts of heating is not available.
Further, even if a system for controlling the amounts of heating has been experientially established about one combination of articles to be brazed together (one combination of articles of certain shapes and certain materials), a different combination of articles will be heated to a different temperature, which would also result in inferior brazing quality.
An object of the present invention is to provide a brazing apparatus and a brazing method in which the brazing quality is not influenced by temperature conditions of the articles to be brazed etc.
To achieve the object shown above, a brazing apparatus according to a first aspect of the present invention comprises: preheating means for preheating articles to be brazed; detecting means for detecting the temperature of the preheated articles to be brazed; heating means for heating the preheated articles to be brazed; control means for controlling the heating means to heat the preheated articles to be brazed to a prescribed temperature on the basis of the detected temperature; and brazing means for brazing the articles to be brazed which have reached the prescribed temperature.
With this structure, the heating means is controlled on the basis of the temperature of the articles measured before they are heated by the heating means.
According to a brazing apparatus of a second aspect of the present invention, in the structure of the first aspect, the control means comprises calculating means for calculating the amount of heating required to heat the articles to be brazed to the prescribed temperature on the basis of their temperature, the calculating means calculating the amount of heating on the basis of conversion data obtained about each of different combinations of articles of different shapes or different materials, and wherein the control means controls the heating means on the basis of the calculated amount of heating.
With this structure, an appropriate amount of heating can be calculated for each combination of articles to be brazed.
According to a brazing apparatus of a third aspect of the present invention, in the structure of the second aspect the conversion data is obtained through a test operation comprising preparing a plurality of sets of articles to be brazed, all of the plurality of sets corresponding to the same combination comprising a first article of a first shape and a first material and a second article of a second shape and a second material, sequentially preheating the plurality of sets of articles to be brazed with the preheating means to different temperatures, detecting the respective temperatures with the detecting means, measuring heating times required to heat the plurality of sets of articles to be brazed with the heating means to the prescribed temperature from the respective temperatures attained by the preheating, and obtaining the data defined by the detected temperatures and the corresponding heating times as the conversion data, and in normal operation, the calculating means calculates the amount of heating from the detected temperature of the articles to be brazed on the basis of corresponding the conversion data.
With this structure, the conversion data can be defined by using the same articles as those which are brazed in actual practice.
According to a brazing apparatus of a fourth aspect of the present invention, in the structure of the third aspect, the conversion data comprises an approximate expression or a conversion table.
With this structure, the amount of heating can be efficiently calculated.
According to a fifth aspect of the present invention, a brazing method comprises the steps of: detecting the temperature of articles to be brazed; heating the articles to be brazed to a prescribed temperature on the basis of the detected temperature; and brazing the heated articles to be brazed.
With this structure, the articles to be brazed are heated on the basis of their temperature measured before they are heated.
According to a sixth aspect of the present invention, a brazing method comprises the steps of: preheating articles to be brazed; detecting the temperature of the preheated articles to be brazed; heating the preheated articles to be brazed to a prescribed temperature on the basis of the detected temperature; and brazing the heated articles to be brazed.
With this structure, the articles to be brazed are heated on the basis of their temperature increased by the preheating and measured prior to the heating.
As shown above, according to the brazing apparatus of the first aspect of the present invention, the heating means is controlled on the basis of the temperature of the articles measured before they are heated, so that the articles to be brazed can be heated accurately to the given temperature to enhance the brazing quality.
According to the brazing apparatus of the second aspect of the present invention, in addition to the effect of the first aspect, the amount of heating can be calculated appropriately for each combination of articles to be brazed, so that the heating means can be controlled stably.
According to the brazing apparatus of the third aspect of the present invention, in addition to the effect of the second aspect, the conversion data is obtained by using the same articles as those brazed in actual practice, so that the articles to be brazed can be accurately heated to the prescribed temperature in normal operation. The brazing quality is therefore not deteriorated even if the articles to be brazed are at different temperatures before heated.
According to the brazing apparatus of the fourth aspect of the present invention, in addition to the effect of the third aspect, the amount of heating can be efficiently calculated, which contributes to automation of the brazing apparatus.
According to the brazing method of the fifth aspect of the invention, the articles to be brazed can be accurately heated on the basis of their temperature measured before they are heated, which enhances the brazing quality.
According to the brazing method of the sixth aspect of the invention, the articles to be brazed can be accurately heated on the basis of their temperature raised by the preheating and measured before the heating, so as to enhance the brazing quality.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.